Pressure responsive indicating instrument



1944- G. E. LINDEMANN 2,340,395

PRESSURE RESPONSIVE INDICATING INSTRUMENT Original Filed Dec. 16, 1939 2Sheets-Sheet l .5. 3O Inven r George E. Lindemcmn by WJMM Q AttorneysPatented Feb. 1, 1944 2,340,395 PRESSURE RESPONSIVE INDICATINGINSTRUMENT George E. Iiindemann, Chicago, Ill., assignor to RepublicFlow Meters Company, Chicago, llL,

a corporation of Illinois Original application December-.16, 1939,Serial No.

309,695. Divided and this application May 16, 1942, Serial No. 443,811

8 Claims.

This invention relates to indicating instruments and more particularlyto instruments responsive to a physical condition to indicate variationstherein. 7

One of the objects of the invention is to provide an indicatinginstrument which may easily and quickly be calibrated to adjust itscharacteristics. According to one important feature calibration may beeiiected by varying the eiiective length of a balancing spring.

Another object of the invention is to provide an indicating instrumentin which the zero position may easily and quickly be set. Preferablythis is done by shifting the balance spring to change its initialtension without changing its characteristics.

Other objects, advantages and novel features of the invention will beapparent from the following description when read in connection with theaccompanying drawings, in which Figure 1 is a side elevation of aninstrument embodying the invention with the cover removed;

Figure 2' is a bottom view of Figure 1;

Figure 3 is a side view looking from the left in Figure 1 with thecasing cut away and with parts in section;

Figure 4 is a section on the line 4-4 of Figure 1;

Figure 5 is a broken section on the line 55 copending application,Serial No. 309,695 flied. December 16, 1939, of which this applicationis a division. The casing comprises a box like casting Ill such as a diecasting having an integral side wall l2 and with its other side open tobe closed by a cover plate 2. The forward face of the casing is closedby a transparent cover l4 curved about a center li'and a pointer arm I!may be pivoted at Ii to swing across the arcuate face of the instrument.A laterally extending pointer 20 is carried by the outer end of the armI! and moves across the face of a translucent curved dial 2!appropriately calibrated. The casing may be mounted by means of a flange2' at the upper end of its arcuate wall and by one or more tappedopenings 29 adjacent the lower end thereof.

In the instrument illustrated a differential pressure such as thatresulting fromdraft may be indicated and for this purpose the casingside wall I! is formed with an inwardly projecting continuous flange illupon which a flexible diaphragm 32 is supported. The diaphragm isinclosed by a cover 34 clamped to the flange 30 by screws 3G to providedifferential pressure chambers on the opposite sides of the diaphragm.Pressure communication with these chambers may be established bypassages 38 and 4| formed in the casing side I! and tapped to receivepressure connections at the bottom of the casing. As shown in Figure 4,the passage 4| has an extension in the cover 34 to communicate with theouter side of the diaphragm.

In order to connect thediaphragm with the pointer II, the diaphragmcarries a stem 16 which projects into an extension II on the cover 34.

The projection 18 has a lateral opening 80, and

a lever 82, having one end pivotally secured to said stem, projectsthrough said opening and is sealed therein by means of a flexiblediaphragm l4. The outer end of the lever 82 is secured to the centralportion of a yoke lijthe legs of which extend along the sides of theprojection 18. Pivots II are threadedly secured in the legs of the yoke86 and are seated in suitable depressions in the sides of projections orlugs 9| integrally formed upon the casting 34. The pivots 88 are alignedsubstantially in the plane of the sealin diaphragm 84. One leg of theyoke 86 projects beyond the respective pivot 88 to form a lever 92 andthis lever is formed with a deep notch 94 extending lengthwise thereoffrom its end and dividing it into two substantially parallel arms. Theends of the arms are formed with opposed fulcrum points 36 which arespaced apart a distance substantially equal to the thickness of a flatmetal balance spring 8|.

The casting 34 is provided adjacent its lower margin with a pair ofprojecting lugs Ill between which a lever III is pivoted. The'lever I02is bent at right angles to form a bell crank. One arm. of the lever isprovided with a longi-- tudinal slot I04 and extendssubstantiallyparallel to the spring SI and the lever 92. The end of the spring 8! issecured to said arm by means of opposed blocks I formed with feathersadapted to seat in said slot and positioned on opposite sides of thearm. A clamping screw III is provided to draw said blocks intoclampingrelation with said arm so that they may be secured in any of severaladjusted positions along said slot. The spring 88 projects between themoved and the spring 98 with a slot I08 adapted to receive a feather andthe bottom of the casing around the adjusting screw H2 and acts to pressthe lever against the nut H0. The feather on the nut prevents it fromturning with the screw when adjustments are to be made.

The pivot 88 opposite the lever 92 is provided with an extension I I6 towhich is secured a lever II8. A link I20 connects the outer end of leverII 8 and the indicator I8 at a point spaced horizontally from its pivot.Since the lever H8 is longer than the radial distance between the axisof indicator I8 and its point of connection to the link I20 angularmovement of the lever II8 will produce a greatly increased movement ofthe indicator I8. The indicator may be counterbalanced by suitableweights I22 mounted upon a threaded extension I24 thereof.

The operation of this instrument is as follows. Diiferential pressuresare applied to the diaphragm through connections to the passages 38 and40, As these pressures vary, the diaphragm moves up or down until thespring 98 exerts a pressure capable of counterbalancing the pressuredifference. The motion of the diaphragm is transmitted to the indicatorI8 through the linkage comprising the lever 82, yoke 86, lever H8, andlink I20, whereby the pointer is moved to indicate the new condition.When it is desired to adjust the zero position of the instrument, knob46 is turned so that the screw H2 is turned to be threaded into or outof the nut IIO whereby the lever I02 is rocked upon its pivots. Thisvaries the pressure which the spring 98 exerts upon the lever 92 for agiven position of the diaphragm whereupon the indicator I 8 may be setto the desired zero position, if identical pressure is admitted to theopposite sides-of the diaphragm through the passages 38 and 40.

If it is desired to change the characteristic of the instrument thecover plate 26 may be remay be shifted by loosening the screw I01 andsliding the blocks I06 along the slot IM-so that a greater or lesslength of the spring extends between said blocks I06 and the fulcrumpoints. If the spring is to b shortened to decrease the sensitivity ofthe instrument the excess or unused portion of the spring merelyprojects into the notch 9i. If the eifective length of the spring is tobe increased, unused portions are withdrawn from the said notch.

Figure 6 illustrates a method of adapting one of these instruments touse with greater pressures, or where less sensitivity is desired. Toaccomplish this purpose, I provide two rings I26 of metal or other solidsubstance which may be placed on opposite sides of the diaphragm toinclose a portion thereof of reduced area, the rings being of suchthickness that they are securely clamped between the walls of thediaphragm casing. Passages I28 may be formed in said rings to permit thepressures transmitted through the passages 38 and ill to be transmittedinto the space inclosed by said rings. It will be seen that the area ofthe diaphragm inclosed by said rings is the only area which is affectedby these pressures to operate the instrument. It will be understood thatthe diaphragm washers must be proportionately reduced in size.

While illustrative embodiments of my invention have been described indetail it is not my intention that the scope of the invention shall belimited to those embodiments or otherwise than by the terms of theappended claims.

What is claimed is:

I. An indicating instrument comprising a condition responsive element, alever pivotally mounted on a fixed axis and connected to the element to.be moved thereby, indicating means connected to the element to beoperated thereby, a flat :balance spring engageable with the end of thelever, a pivotally mounted arm lying substantially parallel to thelever, mounting means for the spring carried by and shiftable lengthwiseof the arm to vary the effective length of the spring, and means toadjust the position of the arm about its pivot to vary the initialloading of the spring.

2. An indicating instrument comprising a condition responsive element, alever pivotally mounted on a fixed axis and connected to the element tobe moved thereby, indicating means connected to the element to beoperated thereby, a fiat balance spring engageable with the end of thelever to oppose movement thereof, a pivoted element, means for swingingthe pivoted element to vary the pressure of the spring on the lever, anda. mounting member for the spring shiftable lengthwise of the lever tovary the eifective length of the spring.

3. An indicating instrument comprising a condition responsive element, apivotally mounted lever connected to the element to 'be moved thereby,indicating means connected to the element to be operated thereby, saidlever being formed with a deep notch in its end dividing it into twoarms having opposed fulcrum points at their ends, a fiat springprojecting into the notch and having its opposite faces engageable withthe fulcrum points respectively to oppose movement of the lever, andmounting means for the spring shiftable lengthwise of the lever to varythe effective length of the spring. a

4. An indicating instrument comprising a condition responsive element, apivotally mounted lever connected to the element to be moved thereby,indicating means connected to the element to be operated thereby, saidlever being formed with a deep notch in its end dividing it into twoarms having opposed fulcrum points at their ends, a flat springprojecting into the notch and having its opposite faces engageable withthe fulcrum points respectively to oppose movement of the lever, apivoted element, means for swinging the pivoted element to vary thepressure of the spring on the lever, and a mounting member for thespring shiftable lengthwise of the lever on the pivoted element to varythe eifective length of the spring.

5. An indicating instrument comprising a diaphragm chamber having acentral projectionjection on a pivotal axis substantially in the planeof the sealing diaphragm, one legof the yoke extending beyond its pivotmounting to provide a lever extension, a fiat spring engaging the leverextension to oppose movement thereof, and mounting means for the springshiftable longitudinally of the lever to vary the effective length ofthe spring.

6. An indicating instrument comprising a diaphragm chamber having acentral projection formed with a lateral opening, a diaphragm in thechamber having a stem extending into the projection, a leverpivotallysecured at one end to said stem and extendingthrough thelateral opening, indicating means connected to the other end of thelever to be operated by movement of the lever, a sealing diaphragmsecured to the lever and around the periphery of the lateral opening, ayoke secured in its central portion to the lever and having its legspivoted outside of the diaphragm chamber on opposite sides of theprojection on a pivotal axis substantially in the plane of the sealingdiaphragm, one leg of the yoke extending beyond its pivot mounting toprovide a lever extension, a flat spring engaging the lever extension tooppose movement thereof, and mounting means for the spring including apivoted element, means for swinging the pivoted element to vary thepressure of the spring on the lever, and a mounting member for thespring shiftable on the pivoted element lengthwise of the leverextension to vary the effective length of the spring.

7. An indicating instrument comprising 9. diaphragm chamber having acentral projection formed with a lateral opening, a diaphragm in thechamber having a stem extending into the projection, a lever pivotallysecured at one end to said stem and extending through the lateral 5opening, indicating means connected to the other end of the lever to beoperated by movement of the lever, a sealing diaphragm secured to thelever and around the periphery of the lateral opening, a yoke secured inits central portion to the lever and having its legs pivoted outside ofthe diaphragm chamber on opposite sides of the projection on a pivotalaxis substantially in the plane 01' the sealing diaphragm, one leg ofthe yoke extending beyond its pivot and having a i notch in its enddividing it into two arms having fulcrum points at their ends, a flatspring projecting into the notch with its opposite faces engaging thefulcrum points to oppose swinging of the yoke, and mounting means forthe spring shiftable longitudinally of said arms to vary the eilectivelength of the spring.

8. An indicating instrument comprising a condition responsive element, alever pivoted on a fixed axis and connected to the element to be movedthereby, indicating means connected to the element to be operatedthereby, a second pivoted lever lying substantially parallel to thefirst named lever, means to adjust the angular position of the secondlever, a flat spring, means adjustably mounting the springfor lengthwiseadjustment along one of the levers, and means adjacent the end of theother lever slidably engaging the spring.

GEORGE E. LINDEMANN.

